This proposal outlines the development of a monitor for routine cardiac output (CO) measurement in pediatric patients in the ICU and during surgery. Presently, no technology is available for this use. Preliminary results using a prototype system in bench, animal, and in clinical trials demonstrated the potential accuracy and usefulness of this technology, and showed that the method did not impose any additional invasiveness to that already existing in the ICU. Five to seven minutes were required for patient connection and measurements. The proposed device uses indicator dilution principles to measure CO. The indicator is isotonic saline (not heat); this allows CO to be measured at peripheral arterial locations, without cardiac catheterization. The proposed device has two options, one uses the existing arterial cannula and venous catheters to create a temporary AV tubing shunt, the second uses tubing connecting arterial cannula to a withdraw/reinfuse syringe pump. Transonic Systems flow/dilution sensor is clipped-onto external tubing, intravenous injections of isotonic saline are performed, and blood is returned to the patient upon completion. In Phase I we propose to further study and validate this technology for use in pediatric surgery and ICU as a simple, routine, inexpensive, and less invasive alternative to currently available technology. PROPOSED COMMERCIAL APPLICATION: The need for a safe and inexpensive CO monitor for the children's ICU and during surgery is vast: while doctors are trained too monitor cardiac parameters on adult patients, no such diagnostic means exist for the pediatric patient. Thus, the potential USA market is all pediatric ICUs and surgical suites. The system may also find use in adult patients as a less expensive and simple alternative to thermodilution without the risks of cardiac catheterization.